Assembling timepiece components by driving them onto each other requires a certain number of precautions. Indeed, numerous components are driven, either onto plates or bars, or onto other intermediate components, particularly in sub-assemblies which are themselves assembled by driving in operations. The stress required to drive in the last component must therefore not be greater than the hold of the weakest component in the stack into which the component is inserted.
This generic problem concerns numerous timepiece assemblies. It will be illustrated here with the example of driving in a centre seconds hand. When this type of hand is driven in, the seconds stone must be held in the gear train bar, to prevent it from moving. Indeed, this is then the worst case scenario where the hold of the stone in its bar is less than the stress necessary to drive in the hand axially. This operation is often hindered by the difficult access to the seconds stone, for example because of the presence of a particular gear train configuration, or an oscillating weight guide element or similar.
JP Utility Model No. 54 157074 U discloses two wheels sets which can move with end-play in relation to each other, and which can both move relative to the same bottom plate.
U.S. patent application Ser. No. 900 380 A in the name of JOST discloses a snap-on cannon-pinion. Elastic components or arm-springs concentrically clamp a first wheel onto the upper shoulder of an arbour, which has a dolly shaped ramp section between two cylindrical sections, when axial stress is exerted as a sleeve is inserted, on the radial supports of these arm-springs, to obtain, in the bottom stop position, a concentric abutment between the sleeve and an arbour carrying a hand.
EP Patent Application No 838 736 A2 in the name of SEIKO does not address any axial shake. It discloses the fixed assembly of a main wheel set on a bar, to act as a means for the internal guiding of a second wheel for the minute display, and for the external and end abutment guiding of a fourth wheel for the seconds display, and also as a spacer between said two wheel sets, particularly to prevent induced vibrations from one to the other. The distal end of the main wheel set includes a groove which cooperates with a shoulder of the fourth wheel.